The invention relates to polymerizing compositions having cationically active and free radically active functional groups.
Acrylate and methacrylate-based compositions polymerize via a one-step free radical mechanism. "Hybrid" compositions featuring both cationically and free radically polymerizable components have been proposed as well. Epoxy resins are typically used as the cationically polymerizable component, and offer the advantage of reduced shrinkage relative to acrylate and methacrylate-based compositions. The hybrid composition polymerizes initially to form a moldable "gel" that can be shaped and compacted. As the polymerization proceeds, the gel forms a hard solid.